1. Field of the Invention
The present invention relates to a system including an external device and its accessories, for use in orthopaedic surgical applications, and more particularly to a method of using the device to reposition and fix one bone segment relative to another bone segment.
2. Background of the Invention
In various orthopaedic applications, it is often necessary to position and secure two bone segments relative to each other. Operative treatment of long bone fractures is a typical example. A variety of techniques are known for holding together the parts of a fractured bone while healing takes place. One such technique is external fixation, in which pins are inserted into the bone on each side of the fracture point, and which are then connected to a frame by adjustable clamps. The clamps can then be tightened to hold the parts of the bone fixed with respect to each other.
Conventional external fixator designs generally lack enough degrees of freedom to facilitate the bone realignment process. For example, U.S. Pat. No. 4,621,627, entitled “External axial fixation device” and issued to DeBastiani et al. on Nov. 11, 1986, and U.S. Pat. No. 5,788,695, entitled “Patient-operated orthopedic devices” and issued to Richardson on Aug. 4, 1998, disclose external fixator designs using two ball-and-socket joints and one telescopic joint and thus may allow three-dimensional adjustment. However, due to the nature of the ball-and-socket joints, controllable adjustments may be difficult. In addition, U.S. Pat. No. 5,662,650, entitled “Method and apparatus for external fixation of large bones” and issued to Bailey et al. on Sep. 2, 1997, discloses an external fixator design using four revolute joints, one central rotary joint, and two telescopic joints and thus may allow three-dimensional adjustment. However, their serrated locking mechanism of the revolute joints does not allow positioning and fixing of the joints at arbitrary positions. Therefore, controllable adjustments may be difficult. In addition, many of the current joint designs do not facilitate direct readout of the joint position. Therefore, controllable adjustments may be even more difficult.
In current clinical practice, fracture reduction using external fixator can be regarded as a trial and error process. Generally, the surgeon is provided with a two-dimensional image obtained by using X-ray or C-arm, based on which image, the surgeon needs to manipulate the fracture site to realign the proximal and distal fragments. This process involves repeated unlocking the fixation joints, manipulating the fracture site, re-locking the fixation joint, and reviewing the static two-dimensional fluoroscopic images. Given that the fracture deformity is three-dimensional in nature, it can be quite difficult to reduce a three-dimensional deformity based on the limited field-of-view and static two-dimensional images. Significant skills may be required by the surgeon to mentally recreate the spatiotemporal relationship between the fracture fragments and maintain eye-hand coordination while performing the adjustments. Furthermore, when the fixation joints are loosened, stability of the configuration so far achieved could be affected. Therefore, such conventional fracture reduction process may be unnecessarily subjective and time-consuming, and the reduction accuracy can be experience-dependent. This process may sometime cause excessive tissue disruptions around the fracture site, which would compromise the tissue integrity and delay fracture healing. Moreover, this process may predispose the surgeons and patients to excessive amount of radiation.